Question 1

Which statement best describes the role of a catalyst in a chemical reaction?

Accepted Answer

A catalyst accelerates the approach to equilibrium without being changed and without altering the reaction's thermodynamic stability.

Question 2

Which of the following is NOT a major class of enzyme?

Accepted Answer

Polymerases

Question 3

The induced fit model of enzyme-substrate interaction differs from the lock-and-key model in that:

Accepted Answer

The enzyme changes its conformation upon substrate binding in the induced fit model.

Question 4

Which mechanism is NOT typically used by enzymes to achieve rate acceleration?

Accepted Answer

Increasing the activation energy of the reaction

Question 5

A patient is diagnosed with a deficiency in thiamine (vitamin B$$_1). $$Which coenzyme function would most likely be impaired?

Accepted Answer

Activation and transfer of aldehydes

Question 6

Which statement about coenzymes is correct?

Accepted Answer

Coenzymes are small molecules that assist enzymes and are not irreversibly changed during catalysis.

Question 7

Which metal ion is important for the catalytic activity of cytochrome oxidase?

Accepted Answer

Copper

Question 8

A competitive inhibitor affects enzyme kinetics by:

Accepted Answer

Binding to the active site and increasing the apparent $$K_m$$ without affecting $$V_{max}.$$

Question 9

Which type of reversible inhibition involves the inhibitor binding only to the enzyme-substrate complex?

Accepted Answer

Uncompetitive inhibition

Question 10

A drug that binds covalently to the active site serine of acetylcholinesterase is best described as:

Accepted Answer

An irreversible inhibitor

Question 11

Which regulatory mechanism is most efficient for maintaining homeostasis in a metabolic pathway?

Accepted Answer

Feedback inhibition at committed steps, often mediated by allosteric enzymes

Question 12

Which statement about allosteric enzymes is TRUE?

Accepted Answer

Allosteric enzymes change conformation upon binding of substrates or effector molecules.

Question 13

Which of the following is an example of reversible covalent modification used to regulate enzyme activity?

Accepted Answer

Phosphorylation by protein kinases

Question 14

Which statement best describes the function of ribozymes?

Accepted Answer

Ribozymes are RNA molecules that catalyze chemical reactions.

Question 15

A researcher observes that an enzyme's activity is increased after phosphorylation and decreased after dephosphorylation. Which enzymes are responsible for these modifications?

Accepted Answer

Kinases add phosphate groups; phosphatases remove them.

Question 16

Which of the following scenarios best illustrates feedback inhibition?

Accepted Answer

The end product of a metabolic pathway inhibits an enzyme at the pathway's committed step.

Question 17

Which coenzyme is derived from niacin (vitamin B$$_3) $$and is involved in oxidation-reduction reactions?

Accepted Answer

Nicotinamide adenine dinucleotide (NAD$$^+)$$

Question 18

Which of the following best explains why substrate level control is considered a crude means of enzyme regulation?

Accepted Answer

It generally requires a large change in substrate concentration to significantly affect enzyme activity.

Question 19

Which type of enzyme inhibition can be overcome by increasing substrate concentration?

Accepted Answer

Competitive inhibition

Question 20

A mutation causes an enzyme to lose its ability to undergo conformational change upon substrate binding. Which model of enzyme-substrate interaction would be most affected?

Accepted Answer

Induced fit model

Enzymes: Biological Catalysts – Structure, Function, and Regulation

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